make scheme and method requirements first-class citizen in Route
added scheme and method setter in RouteCollection
made schemes and methods available in YamlFileLoader
made schemes and methods available in XmlFileLoader

it uses an attribute list instead of multiple scheme/method elements that I also experimented with
[Routing] add support for path-relative and scheme-relative URL generation
[Routing] added tests for generating relative paths and network paths
[Routing] made reference type fully BC and improved phpdoc considerably
fix phpdoc of UrlGeneratorInterface that missed some exceptions and improve language of exception message
[HttpFoundation] Update docblock for non-working method
added changelog entries
[Serializer] Allow options to be passed to SerialiizerInterface#serialize and #unserialize. Thsee options are available to all encoders/decoders/normalizers that implement SerializerAwareInterface.
Fix CS issues, removed global options
Rename $options to $context, as it makes the intent much more clear.
Added context to JsonEncoder
[Form] Deleted references in FormBuilder::getFormConfig() to improve performance
[DependencyInjection] refactored code to avoid logic duplication
Update Ukrainian translation for 2.1 branch
Update Ukrainian translation for master branch
covers edge case for Luhn
merged branch ricardclau/improve-luhn-validator (PR #6591)

This PR was merged into the master branch.

Commits
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b1f190f covers edge case for Luhn

Discussion
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[Validator] Covering edge case for Luhn when checksum is exactly 0

Bug fix: yes
Feature addition: no
Backwards compatibility break: no
Symfony2 tests pass: yes
Fixes the following tickets:
Todo:
License of the code: MIT
Documentation PR:

Actually not a big deal, but a Credit Card with all 0s passed validation. Now this is covered.